<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>元素的增删改</title>
</head>


<body>
    <select id="choose">
        <option>---请选择---</option>
        <option>北京</option>
        <option>上海</option>
        <option>广州</option>
    </select>

    <br>
    <input id="add"><button id="add-btn">add</button>
    <br>
</body>
<script src="Demo.js">

</script>

</html>